Semiconductor light emitting device

ABSTRACT

A semiconductor light emitting device includes a mold resin having a cup shape portion on an upper surface of the mold resin. One or more holes penetrate through the cup shape portion to outside of the mold resin and/or one or more trenches extend from the cup-shaped portion to outside the mold resin. A first lead is provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a first direction, and a second lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction. A light emitting element is mounted on the first lead in the cup shape portion, and a wire electrically connects the light emitting element and the second lead. A sealing resin is embedded in the one or more holes and the one or more trenches and is configured to seal the light emitting element and the wire.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 11/360,521, filed Feb. 24, 2006and claims the benefit of priority under 35 U.S.C. §119 from JapanesePatent Application No. 2005-48312, filed on Feb. 24, 2005, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

SMD (Surface Mounting Device) type semiconductor light emitting deviceshave a wide field of applications since such devices can be surfacemounted to a printed circuit board.

With the application field being broadened, the semiconductor lightemitting device may be used in a wide range ambient temperature. Forexample, in the automotive use, the semiconductor light emitting devicemay be required to be operable in a range of −40-+80 degree Centigrade.

On the other hand, a LED chip, a mold resin, a sealing resin and a metallead frame have a different heat expansion coefficient and a differentYoung's modulus. In case an ambient temperature of the semiconductorlight emitting device is raised and lowered, the sealing resin isexpanded and compressed. So the optical characteristic of thesemiconductor light emitting device may be worsened, or damage, such aspeeling of the sealing resin from another constituent element and/orcracks in the LED chip, may occur in the semiconductor light emittingdevice.

SUMMARY

According to one aspect of the present invention, there is provided asemiconductor light emitting device including a mold resin having a cupshape portion on an upper surface of the mold resin and a holepenetrating through the cup shape portion to outside the mold resin; afirst lead provided in the mold resin and extending from the cup shapeportion to outside of the mold resin in a first direction; a second leadprovided in the mold resin and extending from the cup shape portion tooutside of the mold resin in a second direction which is opposite to thefirst direction; a light emitting element mounted on the first lead inthe cup shape portion; a wire electrically connecting the light emittingelement and the second lead; and a sealing resin configured to seal thelight emitting element and the wire, embedding the hole.

According to another aspect of the present invention, there is provideda semiconductor light emitting device including a mold resin having acup shape portion on an upper surface of the mold resin; a first leadprovided in the mold resin and extending from the cup shape portion tooutside of the mold resin in a first direction; a second lead providedin the mold resin and extending from the cup shape portion to outside ofthe mold resin in a second direction which is opposite to the firstdirection; and the mold resin having a first trench extending from thecup shape portion to outside of the mold resin in a third direction anda second trench extending from the cup shape portion to outside of themold resin in a fourth direction which is opposite to the thirddirection; a light emitting element mounted on the first lead in the cupshape portion; a wire electrically connecting the light emitting elementand the second lead; and a sealing resin configured to seal the lightemitting element and the wire, embedding the first trench and the secondtrench.

According to a further aspect of the present invention, there isprovided a semiconductor light emitting device may include a mold resinhaving a cup shape portion on an upper surface of the mold resin and ahole penetrating from the cup shape portion to a bottom surface of themold resin; a first lead having a first inner lead portion and a firstouter lead portion, the first outer lead portion extending from the cupshape portion to outside of the mold resin in a first direction, thefirst inner lead portion provided in the cup shape portion and beingthicker than the first outer lead portion; a second lead having a secondinner lead portion and a second outer lead portion, the second outerlead portion extending from the cup shape portion to outside of the moldresin in a second direction which is opposite to the first direction,the second inner lead portion provided in the cup shape portion; asemiconductor light emitting element mounted on the first inner leadportion of the first lead; a wire connecting the semiconductor lightemitting element and the second inner lead portion of the second lead; asealing resin configured to seal the light emitting element and thewire, embedding the hole.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a top view of a semiconductor light emitting device inaccordance with a first embodiment of the present invention.

FIG. 2 is a cross sectional view taken along line A-A in FIG. 1.

FIG. 3 is a cross sectional view taken along line B-B in FIG. 1.

FIG. 4 is a cross sectional view taken along line B-B in FIG. 1, showinga heat expansion of a sealing resin in a high temperature.

FIG. 5 is a cross sectional view taken along line B-B in FIG. 1, showinga heat compression of a sealing resin in a low temperature.

FIG. 6 is a top view of a semiconductor light emitting device inaccordance with a comparative example.

FIG. 7 is a cross sectional view taken along line E-E in FIG. 6, showinga heat expansion of a sealing resin in a high temperature.

FIG. 8 is a cross sectional view taken along line E-E in FIG. 6, showinga heat compression of a sealing resin in a low temperature.

FIG. 9 is a top view of a semiconductor light emitting device inaccordance with a second embodiment of the present invention.

FIG. 10 is a cross sectional view taken along line C-C in FIG. 9.

FIG. 11 is an end view of the semiconductor light emitting device shownin FIG. 9.

FIG. 12 is a top view of a semiconductor light emitting device inaccordance with a third embodiment of the present invention.

FIG. 13 is a cross sectional view taken along line D-D in FIG. 12.

FIG. 14 is a top view of a semiconductor light emitting device inaccordance with a fourth embodiment of the present invention.

FIG. 15 is a cross sectional view taken along line F-F in FIG. 12.

FIG. 16 is a cross sectional view taken along line G-G in FIG. 12,showing a heat expansion and compression of a sealing resin in a highand low temperature.

FIG. 17 is a cross sectional view taken along line G-G in FIG. 12,showing a semiconductor light emitting device before applying a sealingresin.

DETAILED DESCRIPTION OF THE INVENTION

Various connections between elements are hereinafter described. It isnoted that these connections are illustrated in general and, unlessspecified otherwise, may be direct or indirect and that thisspecification is not intended to be limiting in this respect.

Embodiments of the present invention will be explained with reference tothe drawings as next described, wherein like reference numeralsdesignate identical or corresponding parts throughout the several views.

FIRST EMBODIMENT

A first embodiment of the present invention will be explainedhereinafter with reference to FIGS. 1-5.

FIG. 1 a top view of a semiconductor light emitting device 100 inaccordance with a first embodiment of the present invention. FIG. 2 is across sectional view taken along line A-A in FIG. 1. FIG. 3 is a crosssectional view taken along line B-B in FIG. 1.

In the semiconductor light emitting device 100, a semiconductor lightemitting element 15 (LED) is mounted on a first lead 13. A firstelectrode (not shown in FIG. 1) provided on a top surface of the LEDchip 15, is connected to a second lead 14 via a bonding wire 16. Thefirst lead 13 and the second lead 14 are molded by a mold resin 11. Themold resin 11 may be formed by, for example an injection mold. The moldresin 11 may be a thermoplastic resin. A cup shape portion 12 isprovided on an upper surface of the mold resin 11 such that an uppersurface of the first lead 13 and the second lead 14 are exposed from themold resin 11. As shown in FIG. 3, the bottom surface of the cup shapeportion 12 is on the substantially same plane as the upper surface ofthe first lead frame 13. The LED chip 15, the first lead 13 and thesecond lead 14 and the wire 16 are sealed by a sealing resin 17. Thesealing resin 17 may be an epoxy resin or a silicone resin. The sealingresin 17 may be preferably transparent to light emitted from the LEDchip 15.

A hole 19 is provided in the mold resin 11. As shown in FIG. 3, the hole19 is penetrating to a bottom surface of the mold resin 11, which is onthe same plane as a bottom surface of the semiconductor light emittingdevice 100. The sealing resin 17 is embedded in the hole 19. Forexample, the sealing resin 17 is introduced into the hole 19 when theLED chip 15 and the wire 16 are sealed by the sealing resin 17.

In FIG. 1, the hole 19 is penetrated from a bottom surface of the cupshape portion 12 to the bottom surface of the mold resin 11. However,the hole 19 may be provided on the slanted portion of the cup shapeportion 12. Furthermore, the hole 19 may be angled from the verticaldirection.

The sealing resin 17 is exposed form the hole 19 to outside of thesemiconductor light emitting device 100. The hole 19 may be formed by ainjection mold of the mold resin 11.

As shown in FIG. 1, two holes 19 is provided upper and below the LEDchip 15. A portion of the first lead 13, on which the LED chip 15 ismounted, is narrower than the other part of the first lead 13.

A damage such as peeling or cracking to the LED chip 15 is reduced by ahole 19 filled with the sealing resin 19 even in case an expansion andcompression cycle occurs in the sealing resin 17.

The mold resin 11 provided under the LED chip 15 may be adapted a goodthermal resistance material. Generally the mold resin 11 is a higherthermal resistance than the sealing resin 17. So the stable operationmay be obtained in a high ambient temperature.

Namely a heat generated by the LED chip 15 is released downward via thefirst lead 13 and the mold resin 11 to outside of the semiconductorlight emitting device 100. This structure is capable of operating in ahigher temperature than a structure having the sealing resin providedunder the LED chip 15. So the maximum operating temperature may beincreased.

The LED chip 15 is explained.

The LED chip 15 may be used an InGaAlP base semiconductor light emittingelement, which emits visible light or an GaN base semiconductor lightemitting element, which emits blue light or ultraviolet light. Aflorescent material such as a phosphor may be dispersed in the sealingresin 17 and a secondary light such as white light may be extracted fromthe semiconductor light emitting device 100.

The function of the hole 19 is explained.

FIGS. 4-5 are cross sectional views taken along line B-B in FIG. 1,showing a heat expansion and a compression of a sealing resin in a highand low ambient temperature.

Generally a Cu board is used as lead frame is about 16.7×10⁻⁶/□ in heatexpansion index and an iron board is used as lead frame is about11.8×10⁻⁶/□ in heat expansion index.

On the other hand, the sealing resin 17 (incase epoxy resin) is about6.3×10⁻⁵/□ in heat expansion index, which is higher heat expansion indexthan a material used as a lead frame.

So as shown in FIG. 4, in a high temperature, the LED chip 15, the firstlead 13, the second lead 14, the wire 16 and the mold resin 11 arepulled by the sealing resin 17. However in this first embodiment, thehole 19 is provided. A tensile stress T is released upward form the cupshape portion 12 and downward from the hole 19. Thus the tensile stressT to the LED chip 15, the wire 16, the first lead 13 and the second lead14 is reduced.

In a low ambient temperature, the LED chip 15, the wire 16, the firstlead 13 and the second lead 14 are compressed by the mold resin 11. Asshown in FIG. 5, in this embodiment, a compression stress C is releasedupward form the cup shape portion 12 and downward from the hole 19. Thusthe compression stress C to the LED chip 15, the wire 16, the first lead13 and the second lead 14 is reduced.

As described above, in this first embodiment, damage to the LED chip 15or the wire 16 is reduced, since the tensile stress T and thecompression stress C are reduced. So peeling or cracking of the LED chip15 may be prevented. The wire 16 is hardly to be cut.

COMPARATIVE EXAMPLE

A comparative example is explained with reference to FIGS. 6-8, whereinFIG. 6 is a top view of a semiconductor light emitting device inaccordance with a comparative example; FIG. 7 is a cross sectional viewtaken along line E-E in FIG. 6, showing a heat expansion of a sealingresin in a high temperature, and FIG. 8 is a cross sectional view takenalong line E-E in FIG. 6, showing a heat compression of a sealing resinin a low temperature.

In this comparative example, the hole 19 is not provided in the moldresin 11. As shown in FIG. 7, the sealing resin 17 is expanded at highambient temperature, so that the expanded sealing resin 17 in the cupshape portion 12 of the mold resin 11 is protruded upward of the cupshape portion 12, and in a bottom of the cup shape portion 12, a tensilestress T to LED chip 15 and a boundary between the wire 16 and thesecond lead 14, which has low heat expansion index, is generated.

As shown in FIG. 8, the sealing resin 17 is compressed and thecompression stress C is generated so that the sealing resin 17 is peeledform the first lead 13 or the second lead 14 in the bottom of the supshape portion 12.

After the heat expansion and compression cycle, the sealing resin 17 maybe peeled from the bottom of the cup shape portion 12. A stress strainto the LED chip 15 may be accumulated. A cracking in the LED chip 15 anda weakening in an adhesive boundary between the lead and the wire mayoccur, especially at the bonding portion on the LED chip 15.

However, in the first embodiment, the hole 19, penetrating from the cupshape portion 12 to the bottom surface of the mold resin 11, is providedin the mold resin 11. So stress may be released to bottom side of themold resin 11, and peeling of the sealing resin 17, cutting of the wire16 or damage to the LED chip 15 may be reduced, in case a wide rangeheat cycle is applied to the semiconductor light emitting device 100.

SECOND EMBODIMENT

A second embodiment is explained with reference to FIGS. 9-11, whereinFIG. 9 is a top view of a semiconductor light emitting device inaccordance with the second embodiment of the present invention, and FIG.10 is a cross sectional view taken along line C-C in FIG. 9, and FIG. 11is an end view of the semiconductor light emitting device shown in FIG.9.

In this second embodiment, trenches 20 are provided in the mold resin11. The trench 20 extends from the cup shape portion to outside of themold resin along the first lead 13 and the second lead 14, respectively.The trenches 20 are provided on the first lead 13 and the second lead14, and in contact with the first lead 13 and the second lead 14,respectively. The sealing resin 17 is embedded in the trenches 20.

Similar to the effect provided by the hole 19 in the first embodiment,the tensile stress T or the compression stress C generated in the cupshape portion 12 is released by the trench 20. A stress along ahorizontal direction, which is generated between the LED chip 15 mountedsurface and the sealing resin 17, is reduced by the trench 20. Thuspeeling of the sealing resin 17, cutting of the wire 16 or damage to theLED chip 15 may be reduced in case a wide range heat cycle is applied tothe semiconductor light emitting device 200.

THIRD EMBODIMENT

A third embodiment is explained with reference to FIGS. 12-13. In thisthird embodiment, a trench 21 is provided in the mold resin 11 in adirection, which is perpendicular to the lead extending direction. Twotrenches 21 extend in a direction perpendicular to the trench 20extending direction. The tensile stress T or the compression stress Cgenerated in the cup shape portion 12 is released by the trenches 20 and21.

Furthermore, the holes 19 are also provided in the mold resin 11. So thetensile stress T or the compression stress C generated in the cup shapeportion 12 is released by the holes 19 and trenches 20 and 21.

The stress generated in the cup shape portion is released in thehorizontal direction by the hole 19. The stress generated in the cupshape portion is released in the vertical direction by the trench 20 and21. Thus the peeling of the sealing resin 17, cutting of the wire 16 ordamage to the LED chip 15 may be reduced in case a wide range heat cycleis added to the semiconductor light emitting device 300.

In the third and the fourth embodiment, the trenches 20 and 21 extendparallel to or perpendicular to the direction in which leads 13 and 14extend. However, the trenches may extend in another direction.

FOURTH EMBODIMENT

A fourth embodiment will be explained with reference to FIGS. 14-17, inwhich FIG. 14 is a top view of a semiconductor light emitting device inaccordance with a fourth embodiment of the present invention; FIG. 15 isa cross sectional view taken along line F-F in FIG. 12; FIG. 16 is across sectional view taken along line G-G in FIG. 12, showing a heatexpansion and compression of a sealing resin in a high and lowtemperature; and FIG. 17 is a cross sectional view taken along line G-Gin FIG. 12, showing a semiconductor light emitting device beforeapplying a sealing resin.

This fourth embodiment is suitable to a high luminosity (high opticaloutput) type semiconductor light emitting device 400.

A first lead 33 and a second lead 34 are made of a high heatconductivity metal. The first lead 33 has an outer lead portion 42 andan inner lead portion 37 which is thicker than the outer lead portion42. A cavity 36, on which the LED chip 15 is mounted, is provided on theinner lead portion of the first lead 33. The LED chip 15 may be mountedon a bottom of the cavity 36 via eutectic solder such as AuSn. A bottomsurface of the first lead 33 and the second lead 34 are exposed to theoutside. A heat sink (not shown in FIGS. 14-17) may be provided on thebottom surface of the first lead 33 and the second lead 34 so that heatgenerated in the LED chip 15 may easily be released to the outside.Light extracted from the semiconductor light emitting device 400 may beincreased by the cavity 36, since light emitted from the LED chip 15 isreflected from an inner surface of the cavity 36.

The mold resin 31 is injection molded. The first lead 33 and the secondlead 34 extend in opposite directions. The cup shape portion 12 isprovided in the mold resin 31. As shown in FIG. 14, a hole 39, which isnot a round shape in the top view, is provided in both sides (upper andbelow) of the first lead 33. Sealing resin 17 is embedded in the holes19.

The diameter at the bottom surface of the cup shape portion 12 alongline G-G is greater than the width of the first lead 13 in the cup shapeportion 12. So the hole 39, which has a semicircle shape in the topview, is provided.

A gap 40 between the first lead 33 and the second lead 34 is embedded bythe mold resin 31. However, the gap 40 may be embedded by the sealingresin 17 or another resin.

The tensile stress T at high temperature and the compression stress C atlow temperature are released via the cup shape portion 12, which opensupward and the hole 39, which opens downward. Thus the peeling of thesealing resin 17, cutting of the wire 16 or damage to the LED chip 15may be reduced, in case a wide range heat cycle is applied to thesemiconductor light emitting device 400.

In this embodiment, a region under the LED chip 15 is the inner leadportion 37 and the sealing resin 17 is not provided under the LED chip15. So the semiconductor light emitting device 400 has good heat releaseefficiency by virtue of the inner lead 37 of the first lead 33 beingexposed to a bottom surface of the semiconductor light emitting device400. Heat generated in the LED chip 15 is easily released to the outsidevia the inner lead 37. So, for example, driving the semiconductor lightemitting device at a higher output may be possible compared to astructure having a sealing resin 17 provided under the LED chip 15. Sothe operating temperature may be improved.

The trenches 20 and 21, which extend in a direction parallel to orperpendicular to the lead extending direction, may be provided in themold resin 31 in a manner similar to the second embodiment or the thirdembodiment. In such a case, the stress generated in the cup shapeportion 12 is reduced.

As described in the first to the fourth embodiments, stress release bymeans of a hole and/or a trench, is provided in a mold resin. Thus thepeeling of the sealing resin 17, cutting of the wire 16 or the damage tothe LED chip 15 may be reduced, in case a wide range heat cycle isapplied to the semiconductor light emitting device.

Furthermore, the shape of the hole in the mold resin is not limited to acircle. The shape of the hole in the mold resin may be oval, semicircle,square, rectangular, polygonal shape or the like, as long as the holepenetrated through the mold resin, as shown, e.g., in FIGS. 16-17.

Likewise, the shape of the cup shape portion in the mold resin is notlimited to a circle, but may also be oval, semicircle, square,rectangular, polygonal shape or the like.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand example embodiments be considered as exemplary only, with a truescope and spirit of the invention being indicated by the following.

1. A semiconductor light emitting device, comprising: a mold resin having a cup shape portion on an upper surface of the mold resin and a hole penetrating through the cup shape portion to outside the mold resin; a first lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a first direction; a second lead provided in the mold resin and extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction; a light emitting element mounted on the first lead in the cup shape portion; a wire electrically connecting the light emitting element and the second lead; and a sealing resin embedded in the hole and configured to seal the light emitting element and the wire.
 2. The semiconductor light emitting device of claim 1, wherein the mold resin has a first trench extending from the cup shape portion to outside of the mold resin in a third direction and a second trench extending from the cup shape portion to outside of the mold resin in a fourth direction which is opposite to the third direction, wherein the sealing resin is embedded in the first trench and the second trench.
 3. A semiconductor light emitting device of claim 2, wherein the first direction is perpendicular to the third direction.
 4. A semiconductor light emitting device of claim 2, wherein the first direction is parallel to the third direction.
 5. A semiconductor light emitting device of claim 2, wherein the mold resin has a third trench extending from the cup shape portion to outside of the mold resin in a fifth direction which is perpendicular to the third direction and a fourth trench extending from the cup shape portion to outside of the mold resin in a sixth direction which is opposite to the fifth direction and perpendicular to the third direction, wherein the sealing resin is embedded in the third trench and the fourth trench are embedded by the sealing resin.
 6. A semiconductor light emitting device of claim 5, wherein the first direction is perpendicular to the third direction.
 7. A semiconductor light emitting device of claim 5, wherein the first direction is parallel to the third direction.
 8. A semiconductor light emitting device of claim 2, wherein the first trench is in contact with the first lead and the second trench is in contact with the second lead.
 9. A semiconductor light emitting device, comprising: a mold resin having a cup shape portion on an upper surface of the mold resin and a hole penetrating through the cup shape portion to outside of the mold resin; a first lead having a first inner lead portion and a first outer lead portion, the first outer lead portion extending from the cup shape portion to outside of the mold resin in a first direction, the first inner lead portion provided in the cup shape portion and being thicker than the first outer lead portion; a second lead having a second inner lead portion and a second outer lead portion, the second outer lead portion extending from the cup shape portion to outside of the mold resin in a second direction which is opposite to the first direction, the second inner lead portion provided in the cup shape portion; a semiconductor light emitting element mounted on the first inner lead portion of the first lead; a wire connecting the semiconductor light emitting element and the second inner lead portion of the second lead; a sealing resin embedded in the hole and configured to seal the light emitting element and the wire.
 10. A semiconductor light emitting device of claim 9, wherein the first inner lead portion of the first lead has a cavity and the light emitting element is mounted on the cavity. 